What are the Branches of Mechanics?

The branches of mechanics more developed and known are statics, dynamics or kinetics and kinematics. Together they make up an area of ​​science related to the behavior of bodily entities at the time of being pushed by powers or landslides..

Likewise, mechanics studies the consequences of bodily entities in their environment. The scientific discipline has its origins in ancient Greece with the writings of Aristotle and Archimedes.

During the early modern period, renowned scientists such as Isaac Newton and Galileo Galilei established what is now known as classical mechanics..

It is a branch of classical physics that deals with atoms that are immobile or that fall slowly, at speeds evidently less than the speed of light.

Historically, classical mechanics came first, while quantum mechanics is a relatively recent invention..

Classical mechanics originated with Isaac Newton's laws of motion while quantum mechanics was discovered in the early 20th century..

The importance of mechanics lies in the fact that, whether it is classical or quantum, it constitutes the most certain knowledge that exists about physical nature and has been especially seen as a model for other so-called exact sciences such as mathematics, physics, chemistry and biology..

Main branches of mechanics

Mechanics have a myriad of uses in the modern world. Her variety of study areas has led her to diversify to encompass the understanding of different themes that underlie other disciplines. Here are the main branches of mechanics.

Static

Statics, in physics, is the branch of mechanics that deals with the powers that operate in immobile bodily entities in equilibrium conditions..

Its foundations were established more than 2,200 years ago by the ancient Greek mathematician Archimedes and others, while studying the force-amplifying characteristics of simple machines such as the lever and shaft..

The methods and results of the science of statics have proven especially useful in the design of buildings, bridges and dams, as well as cranes and other similar mechanical devices..

In order to calculate the dimensions of such structures and machines, architects and engineers must first determine the powers involved in their interconnected parts..

• Static conditions

1. Statics provides the analytical and graphical procedures necessary to identify and describe these unknown forces..
2. Statics assumes that the bodies it deals with are perfectly rigid.
3. He also argues that the addition of all powers operating on an entity at rest must be zero and that there must be no tendency for the forces to rotate the body around any axis..

These three conditions are independent of each other and their expression in mathematical form includes the equations of equilibrium. There are three equations, so only three unknown forces can be calculated.

If there are more than three unknown forces, it means that there are more components in the structure or machine that are required to support the applied loads or that there are more restrictions than are needed to prevent the body from moving..

Such unnecessary components or constraints are called redundant (for example, a table with four legs has one redundant leg) and the method of forces is said to be statically indeterminate..

Dynamic or kinetic

Dynamics is the branch of physical science and subdivision of mechanics that dominates the study of the movement of material objects in relation to the physical factors that affect them: force, mass, impulse, energy..

Kinetics is the branch of classical mechanics that refers to the effect of forces and couples on the movement of bodies that have mass..

Authors who use the term "kinetics" apply dynamics to classical moving body mechanics. This contrasts with statics, which refers to bodies at rest, under equilibrium conditions..

They include, in dynamics or kinetics, the description of the movement in terms of position, velocity and acceleration, apart from the influence of forces, torques and masses.

Authors who do not use the term kinetics divide classical mechanics into kinematics and dynamics, including statics as a special case of dynamics in which the addition of the forces and the sum of the pairs are equal to zero..

You may be interested in 10 Examples of Kinetic Energy in Daily Life.

Kinematics

Kinematics is a branch of physics and a subdivision of classical mechanics related to the geometrically possible movement of a body or system of bodies without considering the forces involved, that is, causes and effects of the movements..

The kinematics aims to provide a description of the spatial position of bodies or systems of material particles, the speed at which the particles are moving (velocity) and the speed at which their velocity is changing (acceleration).

When causal forces are not taken into account, descriptions of motion are only possible for particles that have restricted motion, that is, that move in certain paths. In unrestricted or free motion, forces determine the shape of the path.

For a particle moving along a straight path, a list of corresponding positions and times would constitute a suitable scheme to describe the particle's motion..

A continuous description would require a mathematical formula expressing the position in terms of time..

When a particle moves on a curved path, the description of its position becomes more complicated and requires two or three dimensions..

In such cases, continuous descriptions in the form of a single graph or mathematical formula are not feasible..

• Kinematics example

The position of a particle moving about a circle, for example, can be described by a rotating radius of the circle, like the spoke of a wheel with one end fixed in the center of the circle and the other end attached to the particle..

The radius of rotation is known as the position vector for the particle, and if the angle between it and a fixed radius is known as a function of time, the magnitude of the particle's velocity and acceleration can be calculated..

However, velocity and acceleration have direction and magnitude. Velocity is always tangent to the path, while acceleration has two components, one tangent to the path and the other perpendicular to the tangent..

References

1. Beer, F.P. & Johnston Jr, E.R. (1992). Statics and Mechanics of Materials. McGraw-Hill, Inc.
2. Dugas, Rene. A History of Classical Mechanics. New York, NY: Dover Publications Inc, 1988, pg 19.
3. David L. Goodstein. (2015). Mechanics. August 04, 2017, from Encyclopædia Britannica, inc. Website: britannica.com.
4. The Editors of Encyclopædia Britannica. (2013). Kinematics. August 04, 2017, from Encyclopædia Britannica, inc. Website: britannica.com.
5. The Editors of Encyclopædia Britannica. (2016). Kinetics. August 04, 2017, from Encyclopædia Britannica, inc. Website: britannica.com.
6. The Editors of Encyclopædia Britannica. (2014). Statics. August 04, 2017, from Encyclopædia Britannica, inc. Website: britannica.com.
7. Rana, N.C., and Joag, P.S. Classical Mechanics. West Petal Nagar, New Delhi. Tata McGraw-Hill, 1991, pg 6.